#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long int ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<vvvl> vvvvl;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef vector<vvb> vvvb;
typedef vector<vvvb> vvvvb;
typedef pair<ll,ll> pl;
typedef pair<ll,pl> ppl;
typedef pair<ll,ppl> pppl;
typedef pair<ll,pppl> pppppl;
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define all(a) begin(a),end(a)
#define sz(a) (int)(a).size()
#define F first
#define S second
#define bs(A,x) binary_search(all(A),x)
#define lb(A,x) (ll)(lower_bound(all(A),x)-A.begin())
#define ub(A,x) (ll)(upper_bound(all(A),x)-A.begin())
#define cou(A,x) (ll)(upper_bound(all(A),x)-lower_bound(all(A),x))
template<typename T>using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;
template<class T>bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T&a,T b){if(b<a){a=b;return 1;}return 0;}
//*
using mint=modint998244353;
const ll mod=998244353;
//*/
/*
using mint=modint1000000007;
const ll mod=1000000007;
//*/
//using mint=modint;
//*
typedef vector<mint> vm;
typedef vector<vm> vvm;
typedef vector<vvm> vvvm;
typedef vector<vvvm> vvvvm;
ostream&operator<<(ostream&os,mint a){os<<a.val();return os;}
istream&operator>>(istream&is,mint&a){int x;is>>x;a=mint(x);return is;}
//*/
template<typename T1,typename T2>ostream&operator<<(ostream&os,pair<T1,T2>p){os<<p.F<<" "<<p.S;return os;}
template<typename T1,typename T2>istream&operator>>(istream&is,pair<T1,T2>&p){is>>p.F>>p.S;return is;}
template<typename T>ostream&operator<<(ostream&os,vector<T>v){rep(i,0,sz(v))os<<v[i]<<(i+1!=sz(v)?" ":"");return os;}
template<typename T>istream&operator>>(istream&is,vector<T>&v){for(T&in:v)is>>in;return is;}
template<typename mint>
mint grid_counting(vector<bool>S){
    int N=S.size();
    vector<mint>ex(N+1,1),re(N+1);
    for(int i=1;i<=N;i++)ex[i]=ex[i-1]*i;
    for(int i=0;i<=N;i++)re[i]=1/ex[i];
    vector<int>A(N+1);
    for(int i=0;i<N;i++)A[i+1]=A[i]+S[i];
    function<vector<mint>(int,int,vector<mint>&)>dc=[&](int l,int r,vector<mint>&bottom){
  	    if(r-l==1){
            return S[l]?vm{bottom[1]}:vm{bottom[0],bottom[0]};
  	    }
        int m=(l+r)/2;
        vector<mint>left({bottom.begin(),bottom.begin()+A[m]+1-A[l]}),right({bottom.begin()+A[m]-A[l],bottom.end()});
        auto X=dc(l,m,left);
        int H=m-l-A[m]+A[l],W=A[r]-A[m];
        vector<mint>top(W+1),res(H+1);
        res[0]=right[W];top[0]=X[H];X[0]=right[0]=0;
        if(!W)for(int i=1;i<=H;i++)res[i]=X[i];
        else{
            vector<mint>F(H+W+1);
            for(int i=0;i<=H;i++)F[i]=ex[i+W-1]*re[W-1]*re[i];
            auto G=convolution(X,F);
            for(int i=1;i<=H;i++)res[i]+=G[i];
            for(int i=0;i<=H+W;i++)F[i]=ex[i];
            for(int i=0;i<=W;i++)right[i]*=re[W-i];
            G=convolution(F,right);
            for(int i=0;i<=W;i++)right[i]*=ex[W-i];
            for(int i=1;i<=H;i++)res[i]+=re[i-1]*G[i+W-1];
        }
        if(!H)for(int i=1;i<=W;i++)top[i]=right[i];
        else{
            vector<mint>F(H+W+1);
            for(int i=0;i<=W;i++)F[i]=ex[i+H-1]*re[H-1]*re[i];
            auto G=convolution(right,F);
            for(int i=1;i<=W;i++)top[i]+=G[i];
            for(int i=0;i<=H+W;i++)F[i]=ex[i];
            for(int i=0;i<=H;i++)X[i]*=re[H-i];
            G=convolution(F,X);
            for(int i=0;i<=H;i++)X[i]*=ex[H-i];
            for(int i=1;i<=W;i++)top[i]+=re[i-1]*G[i+H-1];
        }
        auto Y=dc(m,r,top);
        Y.erase(Y.begin());
        res.insert(res.end(),Y.begin(),Y.end());
  	    return res;
    };
    vector<mint>bottom(A[N]+1,1);
    return dc(0,N,bottom).back();
}
int main(){
  cin.tie(0)->sync_with_stdio(0);
  cin.exceptions(cin.failbit);
  string S;cin>>S;
  vector<bool>Q(sz(S));
  rep(i,0,sz(S))Q[i]=(S[i]=='A');
  cout<<grid_counting<mint>(Q)<<endl;
  return 0;
}